njit-etd2003-081 - New Jersey Institute of Technology

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4.1.2.2 Parasympathetic Activity and Sympathovagal Balance Assessment.
1) Rest: Subjects were seated, at rest, and post absorptive for at least four hours, and
refrained from consuming alcohol and caffeinated beverages for at least 12 hours prior
to the test. ECG recordings were made using lead II and lead V, with an
electrocardiographic machine (Marquette Max-1, Marquette Medical Systems,
Milwaukee, WI). The subject's beat-by-beat blood pressure recordings were made using
a wrist cuff via a noninvasive oscillometric device (Model 7000, Colin Medical
Instruments Corp., San Antonio, TX). Blood pressure recordings were made with the
left arm supported at heart level. In addition, respiration was recorded from respiratory
induced temperature changes using a thermistor (YSI reusable temperature probe,
Yellow Springs, OH) placed under the right nostril. During rest subjects were instructed
to maintain normal breathing patterns. Two data gathering episodes were made while
seated in an upright position, each five minutes in duration (one on room air, another on
30% oxygen). Total test duration was approximately 25 minutes (2 trials with
equilibration on oxygen in between).
2) Deep Breathing: Subjects breathed at 0.2 Hz (12 breaths/minute), as this breathing
rate has been shown to stimulate the respiratory sinus arrhythmia, a noninvasive marker
of parasympathetic activity. Subjects were trained until satisfactory tracings were
obtained. This protocol consisted of 2 trials, each of one minute in duration. Total test
duration was approximately 5 minutes (2 trials with rest in between).
3) Valsalva Maneuver: Subjects breathed at a normal rate for 15 seconds, then were
asked to blow against a fixed resistance to a pressure of 20 mm Hg for 15 seconds, and
then were asked to breathe normally for a 30 second interval. Continuous measurement